Process for the production of alkalisoluble cotton textile materials



PROCESS FOR THE PRODUCTION OF ALKALI- SOLUBLE COTTON TEXTILE MATERIALS Robert M. Reinhardt and John D. Reid, New Orleans,

La., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Filed Apr. 11, 1957, Ser. No. 652,321

3 Claims. (Cl. 8-1162) (Granted under Title 35, US. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the production of alkali-soluble cotton textile materials. More specifically this invention describes a process for producing an alkalisoluble cotton textile material that retains the textile properties of the original unmodified material by virtue of an exceedingly mild chemical modification of the original textile material followed by an oxidizing treatment that employs, in combination, two oxidizing reagents in dilute aqueous solution. Oxidation with one oxidizing reagent in combination with a second oxidizing reagent in the practice of this invention is unexpectedly and strikingly synergistic.

11: is well known that certain chemical modifications of cotton such as, for example, carboxymethylation and aminoethylation are elfective for the production of water or alkali-soluble cotton textile material. It is also known that if the chemical modification treatments referred to above are followed by a subsequent oxidizing processing step using organic or inorganic oxidizing reagents, that the ultimate alkali-solubility of the treated material is enhanced to a considerable degree.

Conventional processes for the production of alkalisoluble cotton textile materials with solubilities in excess of 95% involve a chemical modification pretreatment of the textile material to produce a product with a degree of substitution of at least 0.4, followed by a rigorous oxidation treatment using either concentrated oxidizing reagents or, if dilute oxidizing reagents are employed unduly long oxidizing times and high oxidizing temperatures. The combination of chemical modificationto produce' a product with a high degree of substitution. (the average number of ether groups substituted per anhydroglucose unit of the cellulose chain) followed by a vigorous oxidizing step gives rise, in the conventional processes, to serious loss of all desirable textile properties. The object of the present invention is to produce an alkali-soluble cotton textile material by employing '(a) a chemical modification treatment carried to a very low degree of substitution (preferably no more than 0.1) and hence of small import insofar as the original characteristics of the untreated material is concerned and (b) a highly effective oxidation step carriedout by the use, in combination, of two oxidizing reagents. A synergistic effect resulting from the use of mixed oxidizing reagents, permits the use of dilute aqueous oxidizing solutions, low oxidizing temperatures (room temperature), and relatively short treatment times. The combination of the chemical modification to alow degree of substitution and the highly effective oxidation step carried outwith two oxidizing reagents used in relatively low concentrations-which characterizes the process of States Patent ice this invention result in the preservation. in the treated material of substantially all the desirable propertiesv of the originaluntreated textile material.

. The preservation of-the original textilepropertieslin an alkali-soluble textile material is most valuable and highly desirable since, even thoughfor many uses-the presence of the alkali-soluble material is transient, it is essential that the alkali-soluble product, while it exists in textileform, be capable of being processed on conventional textile machines; The obvious requisites are, of course, retention of strength, flexibility and abrasion resistance. A typical use for an alkali-soluble textile material is as a scatfolding or supporting foundation for the preparation of light or novelty yarns and fabrics. By alternating soluble textile yarn with nonsoluble textile yarns in weaving and then subjecting the woven product to dissolution, open-work fabrics and other novelty effects may boxymethylation are employed as the-chezhicaL-modification step as the preferred chemical modification for the process ofthis invention as described in the specific examples that follow. Regardless ofthe chemical modification treatment employed the advantageous feature of the process ofthis inventionis that the chemical modification need not be carried beyond a degree of substitution of about 0.33. The preferred range for this process is a degree of substitution of from about 0.01 to 0.1 average number of aminoethyl or carboxymethyl groups per anhydroglucose unit of the cellulose chain. Aside from the consideration of retaining the'textile'properties of the chemically modified material, the possibility of operating at a low degree of substitution possesses ob= vious economic advantages. Following the chemical modificationstep which step is to produce a material with a low degree of substitution and a materialvirtuallyum changed with respect to textile properties, the chemically modified material is subjected to an oxidation step with a. mixture of chromic and oxalic acid used in combinationin an aqueous solution; .The oxidizing step can. be carried out at any temperature'from 0 to 60? (1., higher temperatures requiring shorter reaction times. The preferred treatment temperature. is room. temperature (20 to 25 C.). The preferred. range of. reagent concentra tion is from'l to 10% by'weight of each reactant (oxalic and chromic acid) inaqueous solution. The-range-0.l% to 50% for chromic acid and from 031% to' saturation foroxalic acid are. operable, the higher" concentrations requiring the shorter reaction times. The oxidizing step when carried out at ro'om'temperature within the preferred concentration range requires from '1 to 51 minutes.

There are three main points of attackby' oxidizing agents on the cellulose'mol ecule: (1) The aldehydic group on carbon atom l of the terminal anhydrogluco'se unit of the cellulose chain; however, in cotton w'ithi'ts' relatively high degree of polymerization the numberof these present is small and of little" importance in this study. (2) The hydroxyl group on carbon atom fo'with formation of aldehyde or carboxyl group, depndingupbn reagent used. (3) The 2,3-dihydroxy or'glycol group which may be oxidized either simultaneously"or 'iiidividin ally without ringcleavage to-form keto'niegroup's er witti ring cleavage to form aldehyde groups. The latter may be further oxidized and converted to carboxyl groups.

Certain reagents in their reaction with cellulose result in almost exclusive oxidation at the 2,3 positions of the glucose residues 'to form aldehyde groups (reducing oxycellulose). The most notable of these reagents are periodic'acid and lead tetraacetate. Chromic acid has been shown to react similarly but not quite as exclusively.

"The most striking of the properties of reducing oxycell-' ulose is alkali-solubility. Since the glycol units of cellulose are trans, complete oxidation is slow, and even'irnpossible at times due to competing side reactions. However, oxidation to the extent of alkali-solubility is readily attained. The mechanism of this alkali-solubility, most widely accepted, is'that of cleavage of the ether linkage beta to the strongly electronegative carbonyl group; The inductive effect of the carbonyl thus causes the hydrogen on the alpha-carbon atom to be removed'by the strong basewhich isiollowed by an electron shift forming a double bond between the alpha. and beta-carbon atoms. with a simultaneous carbon-oxygen .scission.

Partially etherified cottons offer two principal theoretical advantages over untreated cotton for the production of alkali-solublederivatives by oxidation. These advantages are: 1) Presence of solubilizing groups which enhance alkali-solubility through greater solubility of the alkali-cleaved fragments. (2). Opening up ofthe crystalline regions of the fiber for .more uniform andincreased reaction. ,These properties are achieved by variations. in

l the methods; o f-preparation and chemical nature of the substituent group introduced.

Many ethen'fied cottons bear asubstituent group which in itself confers solubility to the derivative. Oxidation of unsubstituted 2,3 glycol units causes alkali-lability. The

' two efiects added together result in high .solubilitygfrom relatively'low degree of reaction. A small amount of oxidation causing a limited amount of cleavage in alkali can. be very eifective if the cleaved fragments hear an alkali-solubilizing group. Thus, fragments of longer chain length than are usually soluble, will go into solution. Therefore, the alkali-solubility of oxidized partially etherified cotton theoretically combines disintegration with true macromolecular solution.

table lists the solubilities of the treated products and the untreated product in hot 10% sodium hydroxide solution.

Although oxidation of cellulose with periodic acid pro l ceeds uniformly throughout the fiber, most other reagents V 'are limited in their reactivity to the accessible regions.

chromic acid, which is preferred for its lower cost and greater availability, is non-swelling and does not penetrate theord'ered regions. 'Many of the .partially 'etherified cottons are prepared underswelling conditions which greatly increase the accessibility of the crystalline regions of the fiber. Thus, inst as'mercerized cellulose is more readily oxidized, the :rate and extent 'of oxidation of many of the etherifiedcottons' are greatly 'increas'ed. V g

' In most cases the two. effects work together,1but' by careful selection and comparison of results, the increase in alkali-solubility due to each can be demonstrated."

Having thus described in a general way the operation of the process of-this invention, details of the process v Example? 1 v 7 7 .Samples of fabrics inform of 8i) x 80'cotton. print cloth were treated as follows: (a) .carboxymethylated by treatment with 17% aqueous chloroaceticjacid and 50% so- The retention of useful textile properties is illustrated by breaking strengths of the alkali-soluble products listed in Table II. Carboxymethylated cotton (degree of substitution=0.095 was oxidized according to the conditions listed in Table II.

TABLE '11 Conditions of Oxidation Percent Percent of Solution kali- Original Solubility 'Breaking 1 Time Temp. 0t 10% Strength. Percent Percent (min.) C.) NaOH) Retained Chromic Oxalic V e Acid Acid 3 i a 1 .25.} 95.0 77 .5 1 3 -'1 1 25v 91.1 88.2

2 2 i l 25 95.6 $4.6 2 0.5 5 25. 91.2 83.7 i 1 5 25 92.2 84. 2

Example 3 The increased effectiveness of aqueous chromic acidoxalicacid solution in contrast to that of chromic acid alone is illustrated by the following data. Samples of carboxymethylated cotton (degree of substitution=0.095)

were treated with 3% by weight aqueous chromic acid solution at 25 C. for periods of 20 minutes and 30 minutes respectively. The sample treated for 20 minutes was partially soluble and the sample treated for 30 minutes was very soluble in hot 10% sodium hydroxide solution. The data in Example 2 show that 'an'oxidation treatment using both chromic acidand oxalic acid in aqueous solution gives rise to a very solubleproduct after I only 1 minute treatment time.

-We claim: a g 1 l. A process for producing a cotton textile material, whichprepared material issubstantially completely soluble in .10% aqueous alkali and which prepared material retains, substantially unaltered, all ,the useful textile properties of the original unmodified material,=-comprisingra mild chemical modification of the original cotton textile material to substitute therein aradical selected from the group consisting ofxaminoethyl and carboxymethyljto a 1 degree of: substitution of aboutfrom 0.01 to 0.1 average dia hy d to. a d e cfi l ti t on. of 0-09 aminoethylated by treatment with 20% aqueous 2-amino' ethyl sulfuric acidand 40% sodium hydroxide to ade-f ltoathe conditions listed inthe. table below,

washed withwaterand dried. The-last" column ;in the number of aminoethyl or. carboxymethyl groups per an: hydroglucose unit of the cellulose chainyand oxidation of the resulting chemically modified cotton textile ma terial for from 1 to 5 minutes atroom temperature with an aqueous solution containing about from ;1 to 3 weight percent of chromic acidan i about from 0.5-to' 3 weight percent of oxalic acid. 7

g 2. A process for producing a cotton textile material, which prepared material is. substantially completely soluble, in 10% aqueous alkali and'which prepared material retains, substantially unaltered, alltheuseful textile properties of the original unmodified material, comprising a frnild v chemical rnodificati on of the. original cotton 'textile.

material by 'carboxymethylation thereof to" a, degreebf substitution of about from 0.01 to 0.1 average number, of carboxymethyl groups per anhydroglucose unit of the cellulose chain, and oxidation of the resulting chemically modified cotton textile material for from 1 to 5 minutes at room temperature with an aqueous solution containing about from 1 to 3 weight percent of chromic acid and about from 0.5 to 3 weight percent of oxalic acid.

3. A process for producing a cotton textile material, which prepared material is substantially completely soluble in 10% aqueous alkali and which prepared material retains, substantially unaltered, all the useful textile properties of the original unmodified material, comprising a mild chemical modification of the original cotton textile material by aminoethylation thereof to a degree of substitution of about from 0.01 to 0.1 average number of aminoethyl groups per anhydroglucose unit of the cellu- References Cited in the tile of this patent UNITED STATES PATENTS 2,422,572 Lilienfeld June 17, 1947 2,724,632 Weisberg Nov. 22, 1955 2,724,633 Daul et al. Nov. 22, 1955 OTHER REFERENCES Guthrie: Introduction of Amino Groups Into Cotton Fabric by Use of Z-Aminoethylsulfuric Acid, Textile lose chain, and oxidation of the resulting chemically 15 Res. 1., November 1947, pp. 625-629. 

1. A PROCESS FOR PRODUCING A COTTON TEXTILE MATERIAL, WHICH PREPARED MATERIAL IS SUBSTANTIALLY COMPLETELY SOLUBLE IN 10% AQUEOUS ALKALI AND WHICH PREPARED MATERIAL RETAINS, SUBSTANTIALLY UNALTERED, ALL THE USEFUL TEXTILE PROPERTIES OF THE ORIGINAL UNMODIFIED MATERIAL, COMPRISING A MILD CHEMICAL MODIFICATION OF THE ORIGINAL COTTON TEXTILE MATERIAL TO SUBSTITUTE THEREIN A RADICAL SELECTED FROM THE GROUP CONSISTING OF AMINOETHYL AND CARBOXYMETHYL TO A DEGREE OF SUBSTITUTION OF ABOUT FROM 0.01 TO 0.1 AVERAGE NUMBER OF AMINOETHYL OR CARBOXYMETHYL GROUPS PER ANHYDROGLUCOSE UNIT OF THE CELLULOSE CHAIN, AND OXIDATION OF THE RESULTING CHEMICALLY MODIFIED COTTON TEXTILE MATERIAL FOR FROM 1 TO 5 MINUTES AT ROOM TEMPERATURE WITH AN AQUEOUS SOLUTION CONTAINING ABOUT FROM 1 TO 3 WEIGHT PERCENT OF CHROMIC ACID AND ABOUT FROM 0.5 TO 3 WEIGHT PERCENT OF OXALIC ACID. 